The invention relates generally to annular apparatus for use in tire monitoring systems and, more specifically, to a tag housing and assembly method for such annular apparatus.
This invention relates to an annular apparatus, including an antenna for electronically transmitting tire or wheel identification or other data at radio frequency. The apparatus includes a radio-frequency transponder comprising an integrated circuit chip having data capacity at least sufficient to retain identification information for the tire or wheel. Other data, such as the inflation pressure of the tire or the temperature of the tire or wheel at the transponder location, can be transmitted by the transponder along with the identification data. The subject invention is specifically directed to an assembly method and tag housing for annular apparatus used in tire monitoring systems.
As is evidenced by the references described below, it is known in the art to employ an annular antenna to transmit, at radio frequencies, data from a transponder contained within the structure of a tire or tire and wheel assembly. In practice, however, it is very difficult to do this with an antenna incorporated into the tire during the course of its manufacture. Both radial ply and bias ply tires undergo a substantial diametric enlargement during the course of manufacture. Bias ply tires are expanded diametrically when inserted into a curing press, which typically has a bladder that forces the green tire into the toroidal shape of the mold enclosing it. Radial ply tires undergo diametric expansion during the tire building or shaping process and a further diametric expansion during the course of curing. Any annular antenna and the electronic circuitry associated therewith built into the tire must be able to maintain structural integrity during the diametric enlargement of the tire during its manufacture. Furthermore, the annular antenna must be able to survive the repeated deformations occurring during tire use and the rigors imparted by testing procedures to which tires are subjected before retreading. Accordingly, a need exists for an annular apparatus and method sufficient to maintain mechanical and structural integrity in the transponder-antenna loop connection during the diametric enlargement of the tire during the building and curing process. In addition, the antenna and the transponder-antenna loop connection must be durable and able to maintain structural integrity throughout the rigors of tire operation and retreading procedures without degradation in performance or malfunction due to breakage of wire or electrical connections.
A magnetic coupling between an antenna and a transponder in an annular assembly is typically effected by means of a toroidal transformer. The antenna is coupled to the transformer by means of a primary winding and the transponder by means of a secondary winding. The mechanical connections of the antenna and transponder to the transformer, however, are subject to failure due to stresses generated in the tire during manufacture or subsequent use. It has been proposed to employ a toroidal transformer body in which the antenna and the transformer are directly coupled by the passage of the antenna directly through the toroid opening. Electrical coupling occurs between the loop and the toroid, and therefore into the secondary winding because the current induced in the loop antenna from the transceiver magnetic field creates a magnetic near the loop. The magnetic field is induced directly into the toroid that closely surrounds the antenna loop wire(s). Such a relationship between the antenna and toroid avoids the problems attendant the prior art that utilize a fixed connection or winding between the antenna and transformer.
It has further been proposed to encapsulate the antenna, transformer, and transponder within an annular strip or ring formed of electrically insulating, elastomeric material. The system components are positioned within a mold and the carrier strip material is induced into the mold and surrounds the components. A unitary annular system is thereby created allowing for convenient integration of the system to a tire by adhesive in a post tire build operation. Encapsulating an antenna, toroidal transformer, and transponder in a carrier strip in order to create the unitary ring assembly, however, carries certain challenges and risks. The relative positions of the antenna, transformer, and transducer must be maintained. Moreover, the integrity of the connections between the associated components must be maintained. In addition, the sensors and communication electronics of the transponder must be protected from damage or contamination due to exposure to the introduction of the carrier strip material.
Accordingly, there is needed a tag housing and assembly method for an annular apparatus including a transponder, transformer, and antenna that facilitates the integration and assembly of the annular apparatus into a carrier strip. The tag housing must serve to maintain the relative orientation of the transponder, transformer, and antenna during their incorporation into a carrier strip or ring; preserve the integrity of the connections between the associated components; and protect the components from damage or contamination from the carrier strip material molded therearound. Moreover, a satisfactory tag housing and assembly method will be economical to fabricate, implement, and deploy and facilitate efficient performance of the transformer, transponder, and antenna in monitoring the condition of a tire.
The subject invention satisfies the need for a tag housing and assembly method for annular apparatus for tire monitoring systems. The tag housing includes a base component having an elongate configuration comprising spaced apart sidewalls, a bottom wall, and end walls that define an internal compartment therebetween. A through bore extends through the end walls and creates with the internal compartment a through passageway through the housing base. A toroidal transformer, in one embodiment, having a through bore is positioned within the housing base component so that the transformer through bore axially aligns with the through bore of the base housing component. A transponder circuit board including sensors and associated electronics is mounted within the internal compartment of the housing base component above the transformer and an electrical coupling is established between the transponder and the transformer. A cap component is provided to enclose the housing and seals against an upper surface of the base component. The cap is generally pyramidal having a lower rim flange, vertical sidewall portions that intersect the rim flange, and upper sidewall portions that taper inward to a flat top surface. The tapered upper portion of the cap defines, generally, the housing xe2x80x9csnoutxe2x80x9d. An aperture or portal is disposed to extend through a median portion of the top surface. The vertical sidewall portions and an upper ledge surface of the rim flange intersect at a substantially right angle.
A coupling of the antenna loop is effected in a coupling with the transformer toroid, preferably, but not necessarily, by passing the antenna loop through the housing through bore to electro-magnetically couple the antenna to the transformer.
The inward taper and stepped profile of the tag housing facilitates a self centering registry of the housing within a mold cavity. The upper ledge surface of the rim flange and the vertical sidewall portions abut against sidewall portions defining the mold cavity to center and isolate the housing snout in a protected region of the mold cavity. The mold is closed and carrier strip material is induced into the mold surrounding a lower portion of the housing and the annular antenna. Pressure from the induced material serves to influence the housing cap into the mold block cavity and further enhances the seal between abutting surfaces of the cap the mold block. The mold block cavity surrounding the port within the upper surface of the cap is thereby maintained in a material free state any entry of carrier strip material through the tag housing port that would otherwise contaminate or damage transponder sensors or electronics is avoided.
In the finished form, the carrier strip, antenna, and tag housing represent a unitary ring assembly that is readily transported, inventoried, handled, and affixed to a tire sidewall by suitable adhesives. The snout of the tag housing extends free of the carrier strip and is positioned by the carrier strip in an exposed relationship with the tire cavity. Consequently, with the annular apparatus attached to a tire liner, the transponder sensors within the housing are in direct communication with the tire cavity through the housing port and a positive and accurate reading of monitored tire cavity parameters is facilitated.
According to another aspect of the invention, the tag housing is elongate and is partially embedded within the carrier strip in either an xe2x80x9con endxe2x80x9d or a xe2x80x9cflatxe2x80x9d orientation. In the xe2x80x9con endxe2x80x9d orientation the tag housing snout projects a relatively greater distance into the tire cavity, but the reduced attachment length along the sidewall radial direction reduces the effect of the rigid tag on tire sidewall bending. In the xe2x80x9cflatxe2x80x9d orientation, the mounted transponder housing assumes a lower profile and the bending influence of centrifugal force on the tag housing from operation of the tire is reduced.
These and other aspects of the invention, which will be apparent to those skilled in the art, are achieved by preferred and alternative embodiments that are described in detail below and illustrated by the accompanying drawings.